Composite optical element and projection optical device

Abstract

A composite optical element is provided. The composite optical element includes a plurality of optical elements, in which at least one of the optical elements is formed of an element modifying an optical path and the other optical elements are bonded to an incident surface and/or exit surface of the element modifying the optical path with a low refractive index material layer in between.

1. A composite optical element comprising:
 a plurality of optical elements, wherein 
 at least one of the optical elements is formed of an element modifying an optical path, and 
 wherein there is at least one optical element bonded to an incident surface and another optical element bonded to an exit surface of the element modifying the optical path with a low refractive index material layer in between each optical element and the element modifying the optical path and further comprising an antireflective film made of an optical film having one or more layers laminated at each surface of the low refractive index material layer that is between each optical element and the element modifying the optical path such that each low refractive index material is located between antireflective films. 
 
     
     
       2. A composite optical element according to  claim 1 , wherein
 the low refractive index material layer has a thickness of λ/4 or more, where λ represents a wavelength of light to be used. 
 
     
     
       3. A composite optical element according to  claim 1 , wherein
 the antireflective films are formed to have a symmetrical film thickness and material with respect to the low refractive index material layer provided in between. 
 
     
     
       4. A composite optical element according to  claim 1 , wherein
 a relationship represented by:
   cos(φ−θ)< nA/nG <cos(θ)
 
 
 is obtained, where nA represents a refractive index of the low refractive index material layer, nG represents a refractive index of the optical element, θ represents a radiation angle of an optical system, and φ represents an angle of the optical path bent by the element modifying the optical path. 
 
     
     
       5. A projection optical device comprising:
 a composite optical element including
 a plurality of optical elements, wherein 
 at least one of the optical elements is formed of an element modifying an optical path, and 
 wherein there is at least one optical element bonded to an incident surface and another optical element bonded to an exit surface of the element modifying the optical path with a low refractive index material layer in between each optical element and the element modifying the optical path and further comprising an antireflective film made of an optical film having one or more layers laminated at each surface of the low refractive index material layer that is between each optical element and the element modifying the optical path such that each low refractive index material is located between antireflective films. 
 
 
     
     
       6. A projection optical device according to  claim 5 , wherein
 the low refractive index material layer has a thickness of λ/4 or more, where λ represents a wavelength of light to be used. 
 
     
     
       7. A projection optical device according to  claim 5 , wherein
 the antireflective films are formed to have a symmetrical film thickness and material with respect to the low refractive index material layer provided in between. 
 
     
     
       8. A projection optical device according to  claim 5 , wherein
 a relationship represented by:
   cos(φ−θ)< nA/nG <cos(θ)
 
 
 is obtained, where nA represents a refractive index of the low refractive index material layer, nG represents a refractive index of the optical element, θ represents a radiation angle of an optical system, and φ represents an angle of the optical path bent by the element modifying the optical path. 
 
     
     
       9. A composite optical element according to  claim 1 , wherein the antireflective films are symmetrically formed at each side of the low refractive index material. 
     
     
       10. A projection optical device according to  claim 5 , wherein the antireflective films are symmetrically formed at each side of the low refractive, index material. 
     
     
       11. A composite optical element according to  claim 1 , wherein the antireflective films are symmetrically formed at each side of the low refractive index material and are comprised of at least one high refractive index film and one low refractive index film. 
     
     
       12. A projection optical device according to  claim 5 , wherein the antireflective films are symmetrically formed at each side of the low refractive index material and are comprised of at least one high refractive index film and one low refractive index film.